Navigation not working after upgrading to Blender 2.79 from 2.78
First, make sure that your numeric keypad is enabled (press the 
Num Lock key).

Also check that you are using the default blender shortcuts: Open the System Preferences (CtrlAltU) and in the input section reset the preset to Blender



Alternatively you can set the keyboard configuration at the splash screen (where it reads "Interaction"
:



Or just use File>Load Factory Settings on the main menu.